GEOLOGY. 145 



that of the mountain tops. It was thus from these that 

 the calcareous precipitation set out. 



662. With each precipitation a greater number of 

 mountain tops made their appearance, because the water 

 sank ; for the calcareous earth is about three times 

 denser than water. 



663. Such being the conditions belonging to the sedi- 

 mentary periods, several consecutive centuries charac- 

 terized by precipitations with repeated recessions and 

 elevations of the water, elapsed and have left evidence of 

 the time thus consumed. 



664. The recession of the water was not always an 

 ebbing or sinking in, but a diminution or disappearance 

 of the same, like the water in a glass lessens in quantity, 

 or becomes thoroughly solid, if salt crystallizes therein. 



665. By such precipitations whole basins of land 

 became dry or freed from sea-water. Streams therefore 

 cf fresh water originated, and with them corresponding 

 organizations. 



666. These streams gradually filled the basins and 

 formed seas. As the seas coalesced by the constantly 

 descending water, an inland sea arose. 



667. This inland sea became again salidified, and 

 that indeed of itself by the influence of light and the 

 dissolution of the salt-banks, which were not overflown. 

 Such is still the Caspian sea and others of that kind. 

 In these marine plants and animals could again originate. 



668. Thereupon new precipitations of salt succeeded, 

 the gypsum and calx being again dissolved, and conse- 

 quently diminutions also of water, whereby rivers again 

 originated. One and the same basin of land was al- 

 ternately covered with fresh and saline water. 



669. Marine and fresh-water animals could therefore 

 originate and perish alternately. And this is the expla- 

 nation of the fact why banks inclosing both kinds of 

 animals are found above and below each other. 



670. An alternating ingress of the sea is not there- 

 fore necessary in all cases to explain the occurrence of 

 marine fossil remains. Such an assumption is also 



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